Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-73550
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-21 20:17:28 UTC
Updated2026-09-21 20:17:28 UTC
DescriptionEnvoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy copies every decoded HTTP/2 Host header value before discarding it when :authority is already present. The discarded value bypasses saveHeader, so its bytes and count are not charged against request header limits. An unauthenticated client can use HPACK indexing to submit many references to a large Host value across a bounded number of streams, forcing extreme header-copy allocation and causing the proxy to be out-of-memory killed. The relevant scope boundary is that the demonstrated amplification uses HTTP/2 HPACK and the duplicate Host discard behavior. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-401 | CWE-401 CWE-401: Missing Release of Memory after Effective Lifetime

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Envoyproxy Envoy affected < 1.36.10 Not specified
CNA Envoyproxy Envoy affected >= 1.37.0, < 1.37.6 Not specified
CNA Envoyproxy Envoy affected >= 1.38.0, < 1.38.4 Not specified
CNA Envoyproxy Envoy affected >= 1.39.0, < 1.39.1 Not specified

References

ReferenceSourceLinkTags
github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b [email protected] github.com
github.com/envoyproxy/envoy/releases/tag/v1.37.6 [email protected] github.com
github.com/envoyproxy/envoy/releases/tag/v1.39.1 [email protected] github.com
github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh [email protected] github.com
github.com/envoyproxy/envoy/releases/tag/v1.36.10 [email protected] github.com
github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2 [email protected] github.com
github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80 [email protected] github.com
github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300 [email protected] github.com
github.com/envoyproxy/envoy/releases/tag/v1.38.4 [email protected] github.com
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